1. Field of the Invention
The present invention relates to a light scanning apparatus and an image forming apparatus including the light scanning apparatus.
2. Description of the Related Art
Hitherto, an image forming apparatus using an electrophotographic printing method includes a light scanning apparatus. The light scanning apparatus scans a uniformly charged surface (scanning surface) of a photosensitive member with a light beam which is modulated according to image information to form an electrostatic latent image on the surface of the photosensitive member. The electrostatic latent image is developed with developer by a developing device to form a toner image. The toner image formed on the photosensitive member is transferred onto a recording medium by a transfer device. The toner image transferred onto the recording medium is fixed to the recording medium by a fixing device, and thus an image is formed on the recording medium.
The light scanning apparatus includes a light source, a deflector, an incident optical system, and an imaging optical system. A light beam emitted from the light source passes through the incident optical system to enter the deflector. The light beam is deflected by the deflector. The deflected light beam is imaged by the imaging optical system as a light spot that scans the photosensitive member at a constant speed. The light source, the deflector, the incident optical system, and the imaging optical system are arranged inside an optical box (hereinafter referred to as “housing”) with accuracy.
In recent years, the following light scanning apparatus is known (Japanese Patent Application Laid-Open No. 2007-121341). In order to cause the light beam to enter the deflector at a predetermined angle, the position of a holding member configured to hold the light source is three-dimensionally adjusted with respect to the housing, and then the holding member is fixed to the housing with an adhesive.
FIG. 11A is a view illustrating a holding member 202 fixed to a housing 203 of a conventional light scanning apparatus. A light source 201 is supported by the holding member 202. The housing 203 is provided with a pair of substantially V-shaped bonding ribs 204 which protrudes from the housing 203.
A method of fixing the holding member 202 to the housing 203 is as follows. First, the holding member 202 is chucked by a jig (not shown). The position of the holding member 202 with respect to the housing 203 in a direction parallel to an optical axis OA of the light source 201 (hereinafter referred to as “optical axis direction B”) is adjusted by moving the jig (not shown) that chucks the holding member 202 in the optical axis direction B. After the position of the holding member 202 with respect to the housing 203 is adjusted, the holding member 202 is fixed to the bonding ribs 204 of the housing 203 with an adhesive 205.
FIG. 11B is a sectional view taken along a plane that passes through the line XIB-XIB and is parallel to a plane orthogonal to the optical axis OA of the light source 201 of FIG. 11A. The holding member 202 is fixed to the pair of substantially V-shaped bonding ribs 204 which protrudes from the housing 203 with the adhesive 205. The adhesive 205 is an ultraviolet curable adhesive. An ultraviolet curable adhesive cures in a short period of time when being irradiated with ultraviolet light. However, an ultraviolet curable adhesive does not cure in a part that is not irradiated with ultraviolet light. Therefore, in order to prevent the ultraviolet light from being blocked by components arranged around the adhesive 205, spaces S1 are provided extending in the vertical direction on both sides of the adhesive 205 so as to enable insertion of ultraviolet irradiation fibers (not shown). Ultraviolet light is radiated from the ultraviolet irradiation fibers (not shown) inserted through the spaces S1 to the adhesive 205 without being blocked by other components. The adhesive 205 that has cured by the ultraviolet light fixes the holding member 202 to the housing 203.
Japanese Patent Application Laid-Open No. 2007-121341 proposes a light scanning apparatus including a plurality of light sources. FIG. 12A is a view illustrating two holding members 302 fixed to a housing 303 of a conventional light scanning apparatus. The two holding members 302 support light sources 301, respectively. FIG. 12B is a sectional view taken along a plane passing through the line XIIB-XIIB of FIG. 12A. The housing 303 has a pair of substantially V-shaped bonding ribs 304 provided thereon. The housing 303 further has a substantially rhombus-shaped bonding rib 306 provided at a center between the pair of bonding ribs 304.
Each of the two light sources 301 is arranged between the substantially V-shaped bonding rib 304 and the substantially rhombus-shaped bonding rib 306. The pair of substantially V-shaped bonding ribs 304, the two light sources 301, and the substantially rhombus-shaped bonding rib 306 are arranged in alignment with one another. An adhesive 305 is applied between the light source 301 and the bonding rib 304 and between the light source 301 and the bonding rib 306.
As illustrated in FIG. 12B, even when the housing 303 includes the plurality of light sources 301, spaces S2 are provided on both sides of the adhesive 305 in the vertical direction so as to enable insertion of the ultraviolet irradiation fibers (not shown). Ultraviolet light is radiated from the ultraviolet irradiation fibers inserted in the spaces S2 to the adhesive 305 without being blocked by other components. The adhesive 305 that has cured by the ultraviolet light fixes the holding member 302 to the housing 303.
In recent years, downsizing of the image forming apparatus has been desired, and hence downsizing of the light scanning apparatus is demanded. However, as illustrated in FIG. 12B, the substantially rhombus-shaped bonding rib 306 is provided between the two light sources 301, and hence it has been difficult to reduce the distance (light source pitch) between the two light sources 301.